The present invention relates to straight edges used as cutting guides, and more specifically to T-squares used in the installation of building panels such as wallboard.
In the construction industry, during the installation of building panels such as gypsum wallboard or the like, installers often need to cut the panels into sizes smaller than the standard 4×8 foot size. To obtain a straight edge on the cut panel, installers traditionally employ metal T-squares. Generally, installers set a sheet of wallboard upright with the rough side facing the installer and place a head of the T-square upon a top edge of the panel. In most cases, the head is oriented horizontally. Next, the typically vertically oriented blade of the T-square is aligned with the line to be cut. The installer then steadies the T-square in position with one hand and with the opposite foot or knee resting against a lower portion of the blade, and runs a utility knife along the side of the T-square from top to bottom to score the cut. After scoring and removing the T-square, the installer applies impact pressure or simply kicks the score to “snap” the drywall. This ensures a clean edge. In some cases, the installer runs the utility knife along the back of the drywall sheet to finish the cut.
When using the guiding edge of conventional T-squares, the user applies an inward lateral pressure to keep the knife against the guide edge. In some cases, this causes the knife to jump over the edge towards the user's hand holding the T-square in position. There have been instances of user's hands being cut due to these knife jumps.
To reduce incidents of such cuts, some installers have fastened a full-length L-shaped metal bracket in the middle of the T-square blade to help guard against accidental knife jumps. Although this design offers added protection to the installer's hand, the raised body of the bracket on the lower two-thirds of the T-square creates an obstacle for users trying to stabilize the bottom of the T-square with their foot or knee. Furthermore, depending on the orientation of the assembly, the full length L-shape design creates a bias for either right or left-handed users. In addition, in some cases the conventional L-brackets obscure the numerical indicia on the T-square, or are uncomfortable for extended use.